Ti₃C₂Tx Nanosheet-Based Electrode with High Capacitance Enabled by Nitrogen Doping and Surface Modification

Owing to its high electrical conductivity, unique layered structure, and strong hydrophilicity, two-dimensional nanomaterial titanium carbide (Ti3C2Tx) has attracted considerable attention as an electrode material for energy storage systems (EESs). However, the applications of Ti3C2Tx in EESs are severely limited by self-restacking and −F surface terminations, which are usually inevitable during the preparation of Ti3C2Tx.To improve the electrochemical performance of Ti3C2Tx, the present authors doped Ti3C2Tx with nitrogen, preparing N–Ti3C2Tx, via thermal decomposition of urea. The interlayer spacing increased from 1.17 nm in Ti3C2Tx to 1.33 nm in N–Ti3C2Tx and the −F surface termination was largely reduced. Benefiting from the synergistic effect of modified surface termination and expanded interlayer spacing, the prepared N–Ti3C2Tx electrode in 1 M H2SO4 delivers a high specific capacitance (390 F g–1) at a current density of 1 A g–1 (approximately twice that of pristine Ti3C2Tx). To demonstrate the effectiveness of the method in other EESs, the Zn2+-storage capacity of the N–Ti3C2Tx electrode was tested in 1 M ZnSO4. The electrode exhibited a capacitance of 252 F g–1 at 1 A g–1, exceeding that of the pristine Ti3C2Tx electrode (212 F g–1). Furthermore, the energy and power densities of the N–Ti3C2Tx // MnO2–CNT system reached 26 W h kg–1 and 950 W kg–1, respectively, much larger than those of the Ti3C2Tx // MnO2–CNT system (13 W h kg–1 and 550 W kg–1, respectively). The proposed strategy can facilely functionalize Ti3C2Tx for use in different high-performing EESs.